Hi Well, both my regular electricians are on holiday and others I've contacted have not replied, so it looks like I may just have to do this job myself. I'd really appreciate some advice from any electricians out there. I am planning to add a double socket near the centre of my living room. This socket is intended for use by a new 2KW electric fire and a plasma TV. My plan is to take a spur from an existing double socket, which is approx 2 metres away. The existing socket has two cables connected and is original wiring and not spurred. I have not checked whether the circuit is a ring or radial - I'm assuming ring, due to the age of the house (11 years) but, as far as I'm aware, that has little bearing in this case (happy to be corrected). The ciruit is proteced by a 32A RCD. I don't know what cable has been used, but I am aware that it's likely to be 2.5mmsq for a ring and 4mmsq for a radial. Either way, I'm not sure I could tell just by looking at it or comparing it with known cable samples. Given the above scenario, is it safe and legal to simply take a spur straight from the socket in 2.5mmsq T&E cable to a new double socket? I am thinking that the spur cable would be protected from overload by the 13A plugtop fuses and from fault by the 32A RCD so a FCU is not required. Assuming the above is OK, I'd appreciate advice about cable rating. Given that I am not sure what cable has been used for the existing circuit, is 2.5mmsq cable OK to use for the spur if it turns out that 4mmsq has been used in the main circuit? As I've said above, I understand the spur would be protected by the 13A plug fuse but I have read that spurs should use the same cable as the rest of the circuit. Should I use 4mmsq cable instead, or is that just as bad if the rest of the circuit is 2.5mmsq? I imagine getting 3 cores of 4mmsq into the socket terminals would be tricky! The spur will run behind plasterboard on a block wall. As it is in a 'safe zone' (horizontally level with existing socket) and the circuit is protected by an RCD, am I correct in thinking that no cable protection is required? - I'd clip the cable to the block wall. One more thing: Am I correct in thinking that this work would not come under part P - i.e. doesn't require inspecting signing off. Thanks for any help you can offer.
When you say spur. A spur is a socket taken off the ring to my knowledge and you can only spur once. So yes you have everything coverd, but I definetly would check it is a ring. See what the Sparks say.
I think he means does he need a 13A spur before the new socket, the answer is no, but he may need one before the original socket if it turns out to already be a spur or spurs. In reality it is probably a socket on the ring wired in 2.5 and it is perfectly acceptable to wire an additional twin from this (as long as there are more ring sockets than spurs for the pedants). However at the very least you should check that its an intact ring you are messing with, especially since you are going to load it with a 2000W fire.
Yes, that's the issue for me. I'm fairly sure what I planned is OK but, for a hefty load like that, I'm not happy about being 'fairly sure'. I asked the same question in an electrician's forum and got some pretty unhelpful answers - I appreciate professional electricians are going to be protective of their trade, but it's a shame they are not prepared to offer any advice at all. I think I might just have to find an electrician for this job after all. I don't mind too much spending the money - especially as it doesn't seem like it would be a long job for a pro; it's just finding someone who is trustworthy and available!
Yes, MCB. The circuit also has RCD protection, which is why I was thinking it did not require cable protection.
To find out if it's a ring, open your consumer unit and locate the MCB which powers the circuit. Then see if that MCB has 2 wires going into it. If it does, then it's a ring, and will be wired with 2.5mm cable. However, if there's only 1 wire, it will be a radial circuit, and will be wired with 4mm cable since your MCB rating is 32amps. Either way, you can add a spur, if you use the correct size wire.
Who's to say the ring hasn't been split along the circuit. Needs a continuity test by a competent sparks. Leave it to those who know.
If its a spur already existing then only one Twin and earth cable will be wired behind the existing 2 gang socket. If it is a rail or ring then there will be two twin and earth cables going in to the back of the existing 2 gang socket. This is not definite assumption to if it is a ring or a rail or a spur as if you have only one twin and earth cable into the back of the socket it could well be the end of the rail as well as a possible spur. A rail for sockets is generally on a rule of thumb wired into 16Amp for 2.5mm2 cable as this is half the 32Amp rating a ring main can provide. If you actually have a ring main it will be wired into a 32Amp MCB/RCD as the current handling of the cable is doubled because it can flow either way around the ring main. A 32Amp MCB/RCD is NOT allowed for a rail installation on 2.5mm2 cable for this purpose. So you can somewhat ascertain vaguely if it is a ring, rail or spur but this is just a rough guide to this. You have to trace the wires in the back of the 2 gang socket you wish to spur from and the wires connecting that sockets ring, rail or spur in the consumer unit and test it. Tedious at the best of times but it has to be done by breaking the input twin and earth at the socket and testing to see if continuity between the first and second leg of the ring main assuming it is a ring main at this point does not exist, make or break the ring at the ganged socket outlet and see if you make or break continuity. This will indicate you have a ring as it is going full circuit. If it is a rail then this test will not show continuity and clearly you will only have one twin and earth going into the consumer unit breaker that SHOULD be a 16 amp. If you have two and it is a rail then scratch your head because there is something wired a miss. If two wires are going into the breaker in the consumer unit and it is not a ring, it could still be a rail but some fool has wired two rails of one breaker or somewhere along the line it was a ring main and someone broke the ring. This is why you must assume nothing and test everything to be sure. Disconnecting the 2 gang socket and spreading the wires apart will effectively break the ring main as it now is not a loop any more. This can be a good test if you have a multimeter with a buzzer on it so you know it is a ring. because you wont get continuity on the two red or black(old colours) blue or brown(new colours) wires inside the consumer unit with the socket removed. Replace the socket and you should get continuity again. Finding out if it is a spur would mean opening up all the further sockets in the vicinity and taking a look to see if you have 3 twin and earth cables in one of them and so on. Investigation and process of analysis is imperative, assume nothing. After you are certain what circuit you are dealing with then proceed to wire in your spur to a ring main, if it is a rail and you have it wired into a 32Amp MCB then for goodness sake change it to a 16Amp even if you give up on wiring the spur in. You can have a rail on 32Amp but you use 6mm2 cable instead and that is a very rare installation method for sure. Be creative but be safe...
Something trains run on. Couldn't agree more. Not only is it not allowed, it isn't manufactured! No such thing as a 32 amp RCD. Complete jibberish! Kind regards
So a MCB on a RCD of a split consumer unit is not manufactured and neither is a 32 Amp MCB or RCBO then? Not a Rail a Radial, freaking spell checker addon to firefox having a ****. I used the simplified method of MCB/RCD to implicate the split consumer unit that is most commonly installed. An MCB on a RCD bus of the consumer unit. All sockets need be RCD protected and each MCB is connected to the RCD so how else would you describe it. He could have RCBO's for all we know. it was easier to just say to a 32amp RCD part of the consumer unit rather than saying 32Amp MCB on a RCD bus of the consumer unit every time i refereed to it. You are being pedantic, talk about clutching at straws.
Forums
Facebook
Twitter
You Tube
Instagram
Shop